The present invention is directed to novel terpolymers emulsion stabilizers for oil-in-water emulsions. In particular, the present invention is directed to the use of terpolymers of water soluble vinyl monomers and water insoluble vinyl monomers having long chain alkyl groups and polymerizable vinyl monomers containing acid groups useful in the formation of stable oil-in-water emulsions. The emulsion stabilizers of the present invention have specific utility in cleaning oil contaminated vessels, oil spill management, pipeline transportation of heavy crude oil drag reduction in pipeline pumping of oil, and enhanced oil recovery by chemical flooding.
The use of ordinary surfactants or emulsifiers to produce stable oil-in-water emulsions has been attempted in the prior art. Ordinary surfactants, generally, are compounds which have a low molecular weight (e.g. less than 30 carbon atoms) and contain hydrophilic (water-loving) and lipophilic (oil-loving) groups. When a mixture of oil and water is mechanically sheared in the presence of these types of surfactants, the surfactants distribute themselves at the oil-water interface as the droplets of oil are formed thus facilitating the formation of an oil-in-water emulsion. Because of the faster mobility of the low molecular weight surfactants, they are quite effective in forming an initial emulsion of the oil and water. However, when the mechanical shear is removed and the emulsion is allowed to stand for some time (i.e. a few hours, days) most emulsions made from this type of surfactant tend to separate. The reason attributed to the separation is that the mobility of the surfactants are such that they move in and out of the surface of the oil droplets leaving some surface area of the oil droplets exposed. Accordingly, when two oil droplets collide at an exposed site, coalescence of the droplets occurs. As time goes on, larger and larger droplets of oil are formed resulting in the separation of the oil phase from the water phase. Accordingly, to stabilize the oil-in-water emulsions the use of a material which is not mobile would be highly desirable.
In U.S. Pat. No. 4,311,832 to Gutnick et. al., a naturally occurring long chained material suitable for emulsions stabilization of oil-in-water emulsions is disclosed. The material is identified as "EMULSAN". The emulsion stabilizer properties of "EMULSAN" arise from its unique structure which consists of a large molecular weight molecule containing both hydrophilic and lipophilic groups. The large molecular weight of the emulsan molecule is such that once the molecules have positioned themselves at the oil water interface they tend to stay there resulting in a highly stable emulsion. While emulsions produced by the use of "EMULSAN" have exhibited high stability they are produced by biotechnological procedures which are relatively inflexible. Accordingly, the "EMULSAN" product cannot be easily modified because of its dependence on bacteria to make the product. Therefore, the use of a synthetic high molecular weight material as a emulsion stabilizer would be preferable because it could be modified or produced by various procedures giving the resulting molecule various properties not possessed by the biotechnological product.
Synthetic polymeric materials having emulsifying properties can be found in the prior art. For example, U.S. Pat. No. 2,816,882 to Schiller discloses polymeric surface active agents comprising copolymers of acrylamide or methacrylamide and acrylic or methacrylic acid esters of a higher molecular weight saturated aliphatic alcohol having at least 8 carbon atoms. In addition, U.S. Pat. Nos. 3,691,124 and 4,464,508 disclosed copolymers of acrylamides for use in water-in-oil emulsion stabilization. Finally, U.S. Pat. Nos. 4,463,151 and 4,463,152 disclose acrylamide acrylate copolymers as viscosification agents. Applicant's invention is directed to terpolymers containing water soluble vinyl monomers and water insoluble vinyl monomers having long chain alkyl groups (C=12-20) and vinyl monomers containing acid groups and their use as emulsifiers and emulsion stabilizers for oil-in-water emulsions.